<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>My Css</title>
    <!--外部样式-->
    <link rel="stylesheet" href="my.css">
    <style>
      /*内部样式*/
      .blue{
        color:blue;
      }
      .green{
        color: green;
      }
      /*标签选择器*/
      h1{
        background-color: chocolate;
      }
      h4{
        color: red;
        font-size: 50px;
      }
      h5{
        color: red;
        text-decoration:underline;
      }
      h6{
        font-size: 50px;
        text-decoration:underline;
      }
      /*id选择器*/
      #aqua{
        color: aqua;
      }
    </style>
</head>
<body>
    <h2 style="color: red">111</h2><!--内嵌样式-->
    <h1 class="blue">222</h1>
    <h2 class="green">333</h2>
    <h1 class="yellow">444</h1>
    <h2 id="aqua">555</h2>
    <h4>段落1</h4>
    <h5>段落2</h5>
    <h6>段落3</h6>
</body>
</html>